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PCM2900C, PCM2706, TUSB2046B, Bus powered, or Self Powered

Ben Palmer
Prodigy 150 points
Other Parts Discussed in Thread: TUSB2046B, PCM2706, PCM2900C

Hi all,


I am starting a project with using the PCM2900C as well as the PCM2706 and the TUSB2046B. And the question I have, is there an advantage to either powering via the USB Bus, or to self power it with a power supply? Thoughts? Suggestions?

Thanks!

Ben

  • 0
    TI__Guru** 100555 points
    Hi Ben,

    Welcome to e2e and thank you for your interest in our products!
    Regarding the Bus-Powered vs Self-Powered, the difference is mostly in sound quality. Self-powered offers slightly better noise performance as you can see in PCM2900C datasheet page 4 "ADC Dynamic Performance" section and PCM2706 datasheet page 3 "Dynamic Performance" section.
    One thing I would like to add here is that you need to make sure that each PCM270x or PCM290x that will be connected to TUSB2046B must have its Max Power Descriptor set to 100mA, not 500mA. PCM2900C don't have problem as its descriptor is set to 100mA. But if you use PCM2706 in Bus-powered mode be sure to set its descriptor to 100mA. If the sum of Max Power of all devices connected to the hub surpasses the capacity of the USB connection the host PC will warn that the hub is not able to power all the devices connected to it.
    Although if you need to set PCM270x or PCM290x descriptor to 500mA you could use TUSB2046B in Self-powered mode, this will remove the limitation previously explained.

    Best regards,
    -Ivan Salazar
    Texas Instruments